Latest research in football - week 29 - 2013

As previous literature updates, we have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Relationship between field performance in high-level soccer playersAuthors: Ingebrigtsen J, Brochmann M, Castagna C, Bradley P, Ade J, Krustrup P, Holtermann A.Reference: J Strength Cond Res. 2013 Jul 8. [Epub ahead of print]Summary: In order to reduce athlete testing time, the aim of this study was to investigate the relationship between the Yo-Yo intermittent recovery test level 1 (IR1) and 2 (IR2)
test performances, maximal sprinting speed (10, 20 and 35 m), repeated sprint ability (RSA) (7x35 m), and sub-maximal heart rates after two and four minutes of the Yo-Yo IR tests by testing 57
high-level soccer players. All players played regularly in one of the three highest levels of Norwegian soccer and were tested during three sessions on three consecutive days. Large correlations
were observed between Yo-Yo IR1 and IR2 test performances (r=0.753 p≤0.05). Small and moderate correlations were found between 20 and 35 m sprinting speed and Yo-Yo IR1 performance (r=-0.289 and
-0.321, respectively, p≤0.05), while 35 m sprinting speed correlated moderately to Yo-Yo IR2 performance (r=-0.371, p≤0.05). RSA at 10, 20 and 35 m all showed moderate to large correlations to
Yo-Yo IR1 performance (r=-0.337 to -0.573, p≤0.05). RSA at 20 m (r = -0.348, p≤0.05) and 35 m (r=-0.552, p≤0.01) correlated moderately and largely to Yo-Yo IR2 performance. Also, moderate and
large correlations were found between sub-maximal Yo-Yo IR1 heart rates after 2 (r=-0.483, p≤0.01) and 4 min (r=-0.655, p≤0.01) and Yo-Yo IR1 performance, and 2 min Yo-Yo IR2 heart rate and Yo-Yo
IR2 performance (r=-0.530, p≤0.01). ICC measures of sub-maximal HR after 2 and 4 min of Yo-Yo IR1 test, and after 2 min of the Yo-Yo IR2 were 0.92 (CV=4.1%, n=33), 0.93 (CV=3.8%, n=33) and 0.72
(CV=2.9%, n=10). Adjusted ordinary least square (OLS) regressions revealed associations (p≤0.05) between sprint speed at 20 m and 35 m and Yo-Yo IR1 test performance, but only between 35 m and
IR2 test performance (p≤0.05). Further, OLS showed that RSA at 35 m was related to both levels of the Yo-Yo IR test (p≤0.01), and that sub-maximal heart rates after 2 and 4 min were independently
associated to Yo-Yo IR1 and IR2 performances (p≤0.01). In conclusion, Yo-Yo IR1 and 2 test performances, as well as sprint and RSA performances, correlated very largely, and it may therefore be
considered using only one of the Yo-Yo tests and a RSA test, in a general soccer-specific field test protocol. The sub-maximal heart rate measures during Yo-Yo tests are reproducible and may be
utilized for frequent, time-efficient and non-exhaustive testing of intermittent exercise capacity of high-level soccer players.

#2 Relative age effect and soccer refereeing: A 'Strategic Adaptation' of relatively younger children?Authors: Delorme N, Radel R, Raspaud M.Reference: Eur J Sport Sci. 2013 Jul;13(4):400-6. doi: 10.1080/17461391.2011.635703. Epub 2011 Dec 5.Summary: Previous research suggested that the relative age effect (RAE) has a psychological influence on children and their decision to engage in a particular sport. Relatively
younger children seem to have lower self-esteem. Indeed, because of the disadvantages of being younger, it is assumed that these players experience more situations of failure and inferiority.
Because of these negative performance cues, it is likely that these young players feel less competent, which eventually leads to a higher dropout rate. These children can also decide to
participate in sports in which physical attributes are less important. This shift from one sport to another can be interpreted as a 'strategic adaptation'. The purpose of this study was thus to
investigate whether refereeing could be another form of 'strategic adaptation'. If a child chooses a specific sport but then does not feel competent enough to be a player, refereeing might be an
alternate path followed to stay in the environment of a sport they like. Given the minimal age limits for refereeing, two hypotheses were formulated: (1) 'reversed' RAE would be observed in
district referees younger than 18 years old and (2) no RAE would be observed in district referees older than 18 years old, regional referees and national referees. The birthdates of all official
male soccer referees (n=13,952) were collected from the federation database. Results show that the distribution of all district referees was significantly unbalanced (χ(2)=18.73, df=3,
P<0.001) with an over-representation of individuals who were born in the second half of the competitive year. As expected, this imbalance was exclusively located in district referees of 18
years old and less (χ(2)=8.03, df=3, P<0.05), while the distribution was uniform for adults (χ(2)=5.17, df=3, P<0.16). Concerning regional referees (χ(2)=2.09, df=3, P<0.554) and
national referees (χ(2)=3.75, df=3, P<0.290), the results also provide support for our initial hypothesis as uniform distributions were found for both groups. This study brings to light new
elements in the potential relationship between relative age and refereeing. Qualitative and/or longitudinal research is needed to confirm our quantitative data.

#3 Relative age effects in Swiss junior soccer and their relationship with playing positionAuthors: Romann M, Fuchslocher J.References: Eur J Sport Sci. 2013 Jul;13(4):356-63. doi: 10.1080/17461391.2011.635699. Epub 2011 Dec Summary: Relative age effects (RAEs) refer to age
differences between children in the same selection year. The present study investigated the prevalence of RAEs and their link to playing positions in Swiss junior soccer. Swiss male junior soccer
players (n=50,581) representing 11% of the age-matched population - members of extra-curricular soccer teams - were evaluated to determine the influence of RAEs on Swiss junior soccer. Subgroups
were the national talent development programme (n=2880), and U-15 to U-21 national teams (n=630). While no RAEs were found for the self-selected extra-curricular soccer teams or for the U-20
teams (P>0.05), significant RAEs were found for talent development and the national U-15 to U-19 and U-21 teams (P<0.01). Additionally, defenders born early in the year were significantly
overrepresented compared with goalkeepers, midfielders and strikers (P<0.05). In Switzerland, RAEs apparently have substantial influence on the talent identification process for U-15 to U-18
teams, significantly influencing the selection of players in talent development teams already at an early age, but do not influence self-selected participation in extra-curricular soccer.
Additionally, the RAE bias may be a predictor of playing positions in national teams. To minimise RAEs in Swiss soccer, systematic education for all coaches regarding RAEs should be established,
in addition to a slotting system with rotating calendar cut-off dates.

#4 Mental rotation performance in soccer players and gymnasts in an object-based mental rotation taskAuthors: Jansen P, Lehmann J.Reference: Adv Cogn Psychol. 2013 Jun 17;9(2):92-8. doi: 10.2478/v10053-008-0135-8. Print 2013.Summary: In this study, the effect of motor expertise on an object-based mental rotation task was investigated. 60 males and 60 females (40 soccer players, 40 gymnasts, and 40
non-athletes, equivalent males and females in each group) solved a psychometric mental rotation task with both cube and human figures. The results revealed that all participants had a higher
mental rotation accuracy for human figures compared to cubed figures, that the gender difference was reduced with human figures, and that gymnasts demonstrated a better mental rotation
performance than non-athletes. The results are discussed against the background of the existing literature on motor experts, mental rotation performance as well as the importance of the testing
situation and the test construction.

#5 A psychometric evaluation of the Group Environment Questionnaire in a sample of professional basketball and soccer
playersAuthors: Steca P, Pala AN, Greco A, Monzani D, D'Addario M.Reference: Percept Mot Skills. 2013 Feb;116(1):262-71.Summary: Psychometric properties of the Group Environment Questionnaire were investigated in a large sample of soccer (n = 222) and professional basketball players (n = 375).
Confirmatory factor analysis was performed both on the total sample and on the two subsamples through a multi-group approach; associations between cohesion and the duration of belonging to the
team were also explored. Results confirmed the four-factor structure proposed by Carron's original model even though some items with low loadings were eliminated. No significant associations were
found between team cohesion and the duration of belonging to the team.